The US Senate majority leader Tom Daschle says he intends to push quickly for a vote on setting up an independent commission to investigate possible intelligence failures prior to the 11 September attacks.

They inevitably are going to get their hands on them and they would not hesitate one minute to use them

Donald Rumsfeld

Mr Daschle said he wants outside experts to collect and review possible warning signs that were missed.

President Bush, who has come under strong criticism over FBI memos that were apparently not followed up, says the intelligence committees already at work are the best way to proceed.

Separately, US Defence Secretary Donald Rumsfeld has also said it is "inevitable" terrorists will acquire weapons of mass destruction.

His comments come amid warnings from the US Government of possible further terror attacks on American soil.

In New York, security has been tightened around the city's landmarks, including the Statue of Liberty and the Brooklyn Bridge, following warnings from the FBI they may be the target of attacks.

Rumsfeld said states could equip terrorists

Police Commissioner Raymond Kelly said the FBI's joint terrorism task force in New York received information about "general threats" based on interviews with people detained after the 11 September attacks.

Secretary of State Colin Powell said on Tuesday he believed terrorists "are trying every way they can to get their hands on weapons of mass destruction, whether radiological, chemical, biological or nuclear".

Mr Powell was speaking a day after FBI Director Robert Mueller warned it was "inevitable" that suicide bombers would strike the US sooner or later, while on Sunday Vice-President Dick Cheney said more terror attacks on America were "almost certain".

Iran accused

Earlier, the US State Department issued its annual report on global terrorism, accusing Iran of being the most active sponsor of state terrorism in the world.

In its report to Congress, the State Department listed Iran, Sudan, Libya, Iraq, North Korea, Cuba and Syria as supporters of terrorism for the eighth year running.

Blacklisted states

Iran

Sudan

Libya

Iraq

North Korea

Cuba

Syria

The Patterns of Global Terrorism report called the 11 September suicide attacks on New York and Washington "the worst international terrorist attack ever", killing nationals from more than 78 countries.

The annual report was the first issued since President George W Bush declared war on global terrorism and demanded states take action against extremist groups.

The report found that while Iran had reduced its involvement in some areas of terrorist activity, its support for militant groups opposed to Israel had intensified.

The new US accusations against Iran have been dismissed as irresponsible by a senior Iranian official. He was quoted by the Associated Press as saying they further damaged any chances of establishing ties between Washington and Tehran.